package com.mysite.seckill.web.util;

import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

/**
 * AES 加密与解密
 */
public class CipherUtil {

    private static final String SECRET_KEY_STR = "DF8Sas%fd#gl";

    /**
     * 加密
     *
     * @param content         需要加密的内容
     * @param secretKeyString 加密密码
     * @return
     */
    private static byte[] encrypt(String content, String secretKeyString) {
        try {
            KeyGenerator kgen = KeyGenerator.getInstance("AES");
            SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG", "SUN");
            secureRandom.setSeed(secretKeyString.getBytes("UTF-8"));
            kgen.init(128, secureRandom);
            SecretKey secretKey = kgen.generateKey();
            byte[] enCodeFormat = secretKey.getEncoded();
            SecretKeySpec key = new SecretKeySpec(enCodeFormat, "AES");
            Cipher cipher = Cipher.getInstance("AES");// 创建密码器
            byte[] byteContent = content.getBytes("utf-8");
            cipher.init(Cipher.ENCRYPT_MODE, key);// 初始化
            byte[] result = cipher.doFinal(byteContent);
            return result; // 加密
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 解密
     *
     * @param content         待解密内容
     * @param secretKeyString 解密密钥
     * @return
     */
    private static byte[] decrypt(byte[] content, String secretKeyString) {
        try {
            KeyGenerator kgen = KeyGenerator.getInstance("AES");
            SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG", "SUN");
            secureRandom.setSeed(secretKeyString.getBytes("UTF-8"));
            kgen.init(128, secureRandom);
            SecretKey secretKey = kgen.generateKey();
            byte[] enCodeFormat = secretKey.getEncoded();
            SecretKeySpec key = new SecretKeySpec(enCodeFormat, "AES");
            Cipher cipher = Cipher.getInstance("AES");// 创建密码器
            cipher.init(Cipher.DECRYPT_MODE, key);// 初始化
            byte[] result = cipher.doFinal(content);
            return result; // 加密
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 将二进制转换成16进制
     *
     * @param buf
     * @return
     */
    private static String parseByte2HexStr(byte buf[]) {
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < buf.length; i++) {
            String hex = Integer.toHexString(buf[i] & 0xFF);
            if (hex.length() == 1) {
                hex = '0' + hex;
            }
            sb.append(hex.toUpperCase());
        }
        return sb.toString();
    }

    /**
     * 将16进制转换为二进制
     *
     * @param hexStr
     * @return
     */
    private static byte[] parseHexStr2Byte(String hexStr) {
        if (hexStr.length() < 1)
            return null;
        byte[] result = new byte[hexStr.length() / 2];
        for (int i = 0; i < hexStr.length() / 2; i++) {
            int high = Integer.parseInt(hexStr.substring(i * 2, i * 2 + 1), 16);
            int low = Integer.parseInt(hexStr.substring(i * 2 + 1, i * 2 + 2), 16);
            result[i] = (byte) (high * 16 + low);
        }
        return result;
    }

    /**
     * 加密
     *
     * @param content 需要加密的内容
     * @return 加密后的字符串
     */
    public static String encode(String content) {
        byte[] encryptResult = encrypt(content, SECRET_KEY_STR);
        return parseByte2HexStr(encryptResult);
    }

    /**
     * 解密
     *
     * @param password 需要解密的字符串
     * @return 解密后的字符串
     */
    public static String decode(String password) {
        byte[] decryptFrom = parseHexStr2Byte(password);
        byte[] decryptResult = decrypt(decryptFrom, SECRET_KEY_STR);
        return new String(decryptResult);
    }

    public static void main(String[] args) {
        String content = "123456";
        System.out.println("加密前：" + content);

        String ciphertext = encode(content);
        System.out.println("加密后：" + ciphertext);

        String cleartext = decode(ciphertext);
        System.out.println("解密后：" + cleartext);
    }
}
